This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A222203 #19 Jan 01 2019 06:31:06 %S A222203 1,3,54,1140,99051,13049563,6044482889,4738211572702, %T A222203 11986520595161863,54755153078468134960,764291947227525464744293, %U A222203 20119942924108379011391597989,1558052539448513320447263528275071,234788223520702255614480389250160811898,101199388044301804167035198499446336399419451,86918369741985767628242106496018767545685968221295 %N A222203 Number of ways to cover the n X n+1 grid graph by vertex disjoint cycles. %H A222203 Andrew Howroyd, <a href="/A222203/b222203.txt">Table of n, a(n) for n = 2..24</a> %H A222203 Peter Tittmann, <a href="http://web.archive.org/web/20070715034048/http://www.htwm.de/~peter/research/enumeration.html">Enumeration in graphs: counting Hamiltonian cycles</a> [Archived link] %H A222203 Robert Israel, <a href="/A222203/a222203.pdf">The 54 solutions for n=4</a> %Y A222203 Cf. A222202, A222204. %K A222203 nonn %O A222203 2,2 %A A222203 _N. J. A. Sloane_, Feb 14 2013